1. Field of the Invention
The present invention relates generally to integrated circuit (IC) testing, and in particular is concerned with an apparatus for burn-in of integrated circuits mounted on a carrier tape.
2. Description of the Prior Art
A known method of bonding and packaging integrated circuits or chips is tape automated bonding or "TAB". In this method, chips are bonded to a carrier tape to form a supply. The tapes are stored on reels for use in automated operations in known manners.
Generally, the carrier tapes range in width from 8 mm. to 70 mm. and are multi-layered structures with an insulating film base and a conductive layer (typically gold-plated copper). Desired patterns are formed in the tape to define chip mounting locations on the tape. The conductive layer is patterned to define leads which will make contact with the chip and then fan out. An IC chip is positioned adjacent the mounting location so that chip contact pads are aligned with the leads. In a single operation, all pads are thermally bonded to their respective leads simultaneously.
The TAB process provides a convenient way of handling IC components in automated assembly operations. The webs of tape with mounted ICs may be wound as reels and may be transported to desired locations for testing and assembly and the like. Utilization of a TAB system provides an economical and reliable means of assembling, bonding, and handling integrated circuits.
It is common to perform "burn-in" of integrated circuit (IC) chips by subjecting the chips to elevated temperatures for an extended period of time while electrically exercising them. This may involve either dynamic or static exercising of the IC chips. The purpose of burn-in is to cause failure of those chips which would exhibit an unacceptably short life in normal operation. Any chip which fails during burn-in is weeded out as a reject during subsequent testing, after the chip has been removed from the burn-in environment.
In the past, this burn-in procedure has been performed by mounting the ICs in individual sockets of a burn-in circuit board. This has required, in the case of ICs mounted on tape using a TAB process, that the ICs be severed from the tape at the time of burn-in, and that the ICs be handled individually thereafter.